This invention relates to sulfonated xanthene dyes, and to photographic products and processes using these dyes.
It is well known that photographic film, especially multicolor film, may and generally does vary from lot to lot, notwithstanding efforts to "repeat" previous films. Manufacturers of multicolor photographic film have developed a number of procedures to minimize the effects upon the final multicolor image of unavoidable variations in manufacturing operations. These variations are reflected primarily in shifts in color balance as reflected in mismatching of the D log E curves of the individual red, green and blue exposures. Equipment used to coat multicolor film is highly precise but variations from the intended coverage of silver halide and/or the dye image-forming materials do occur. Repeat batches of silver halide emulsions may, and usually do, vary in their photographic response. Individual layers may be dried to slightly different degrees. Film is stored for a period of time after coating to allow the films to "age", so that changes in sensitometry following coating have an opportunity to reach a plateau prior to sale. If the film is designed to be developed by a photofinisher or in a darkroom, processing of the exposed multicolor film is controlled within very narrow limits, typically within .+-.0.5.degree. C. from a prescribed temperature, in order to minimize sensitometric variations from film to film. Where the multicolor film is of the negative type, an opportunity to adjust the sensitometry occurs in printing the desired final positive image, during which operation the printing exposure may be appropriately color filtered.
The basic sources of sensitometric variations noted above exist also in multicolor diffusion transfer films, with the added complication that once the film is shipped, the sensitometric properties are essentially fixed. The opportunity for adjustment provided in darkroom processing, practically speaking, is not available for users of self-developing films. While professional and advanced amateur photographers may be skillful enough to utilize color correction filters to at least partially "rebalance" the color balance, ordinary users of the film would only be confused by such additional operations.
It is well known to use a light-screening dye in a photographic product. Such a dye may be incorporated as a filter dye in a light-sensitive emulsion layer, in a layer coated over one or more light-sensitive emulsion layers, or between two differently color-sensitized emulsion layers, to modify the light record in the emulsion layer or to control the spectral composition of light falling on an underlying light-sensitive layer, or it may be incorporated as an antihalation dye in a non-light-sensitive layer positioned on either side of a support carrying the light-sensitive layer(s).
The dye employed for these purposes, in addition to having the requisite spectral absorption characteristics for its intended use, should be photochemically inert, that is, it should not have any adverse effect on the properties of the light-sensitive emulsion layer(s), and it should be capable of being decolorized or removed during photographic processing so as not to leave stain in the processed photographic product. Even in photographic processes where the dye is removed by being dissolved in a processing solution, it is also usually preferred that the dye decolorize in order to avoid contamination of the processing solution and to prevent staining from residual dye in the processed photographic product.
Although various classes of dyes have been proposed for use in antihalation and color correction filter layers, many of the dyes heretofore employed have not been altogether satisfactory. Some of the dyes tend to reduce sensitivity, fog or exert other adverse effect on the photographic product. However, the major drawback of many dyes previously employed is their tendency to cause stain due to incomplete decolorization or reversal of some of the decolorized form to the original colored form. For example, some classes of dyes rely on the presence of a reagent, such as a sulfite, for "bleaching", i.e., decolorization, and unless the dye is removed from the photographic product during or after processing, its color may reappear in time as the decolorized dye is slowly re-oxidized.
Among the classes of light-screening dyes used previously are the triarylmethanes and xanthenes. For example, U.S. Pat. Nos. 1,879,537; 1,994,876; 2,350,090 and 3,005,711 disclose the use of fuchsone-type dyes in antihalation layers, and U.S. Pat. Nos. 3,406,069 and 3,615,548 are concerned with the metal chelates of fuchsone dyes as antihalation dyes. These and other types of triarylmethane dyes suffer from one or more of the drawbacks discussed above, and in particular, prior dyes of this type have been difficult to keep decolorized at the pH's normally encountered during processing subsequent to "bleaching" and in the final product. Xanthenes have been employed in antihalation layers that are removed during photographic processing. For example, U.S. Pat. Nos. 2,182,794; 2,203,767 and 2,203,768 disclose the use of rhodamine dyes in certain antihalation layers that are removed during processing in an acid bath or a plain water rinse bath depending upon the solubility characteristics of the particular layer.
U.S. Pat. No. 4,258,118, issued Mar. 24, 1981 to James W. Foley, Louis Locatell, Jr. and Charles M. Zepp, and assigned to the same assignee as the present application, describes certain 3,6-bis-indolinoxanthene derivatives, which find utility as photographic light-screening dyes and offer advantages over the light-screening dyes previously used because of their ability to decolorize completely and irreversibly to a substantially inert colorless product. Specifically, the dyes disclosed and claimed in this patent comprise xanthene derivatives having cations of the formula: ##STR2## in which X is an --SO.sub.2 --N(R')--COCH.sub.3 or --SO.sub.2 -N(R')--CO.sub.2 (CH.sub.2).sub.2 Y grouping, wherein R' is an alkyl group and Y is an electron-withdrawing group.
These dyes suffer, however, from the disadvantage their wavelength of maximum absorption (.lambda..sub.max) undergoes substantial shifts in the presence of certain wetting agents and polymeric binders; in extreme cases, the absorption may even be shifted into the near infra-red, thereby rendering the dyes unsuitable for use in conventional photographic products sensitive to visible light. In addition, these dyes are difficult to disperse in certain media.
U.S. Pat. No. 4,258,119, and U.S. Pat. No. 4,290,950, both to Cournoyer et al. and assigned to the same assignee as the present application, describe sulfonated derivatives of the dyes described in the aforementioned U.S. Pat. No. 4,258,118; the disclosures of these patents are herein incorporated by reference. These sulfonated dyes, which are stated in Pat. Nos. 4,258,119 and 4,290,950, to be of the formula: ##STR3## in which X is as defined above and A is a hydrogen atom or an --SO.sub.3 H group, have recently been found to be of the formula: ##STR4## in which X and A are as defined above. These sulfonated dyes do not undergo the shifts in .lambda..sub.max in polymeric media which the unsulfonated dyes do. However, these sulfonated derivatives do undergo very slow conversion to the uncolored form of the dye during storage of photographic products containing these dyes, and this slow conversion may limit the shelf-life of such photographic products. Furthermore, when these sulfonated dyes are used in self-developing photographic products, in practice it is typically necessary to coat the dyes from a mixture of water and trifluoroethanol to prevent agglomeration of the dyes upon contact with the mordant. Trifluoroethanol is highly acutely toxic, a severe irritant, can cause tissue damage and pulmonary edema, and is also known to have undesirable effects on the male reproductive system. Accordingly, it is highly desirable to eliminate this solvent from manufacturing operations.
Accordingly, there is a need for dyes having similar properties to those disclosed in the aforementioned U.S. Pat. Nos. 4,258,119 and 4,290,950, but which have greater storage stability and which can be coated without the use of toxic solvents. The present invention provides dyes meeting these requirements.